execline is a very light, non-interactive
scripting language, which is similar to a shell.
Simple shell scripts can be easily rewritten in
the execline language, improving performance
and memory usage. execline was designed for
use in embedded systems, but works on most
Unix flavors.

skalibs is a set of general-purpose, low-level C libraries, all in the public domain. It can replace or hide the standard C library to some extent. It is designed to allow building of small static binaries. It is used in building all skarnet.org software, including execline and s6.

iodine lets you tunnel IPv4 data through a DNS server. This can be useful in situations where Internet access is firewalled, but DNS queries are allowed. It needs a TUN/TAP device to operate. The bandwidth is asymmetrical with limited upstream and up to 1 Mbit/s downstream.

Avian is a lightweight virtual machine and class
library, both written from scratch to provide a
useful subset of Java's features. It's well-suited
to cross-platform applications which need a
typesafe language but must remain small and
self-contained.

Werc is a minimalistic RESTful Web application framework and content management system. It follows the Unix "tool philosophy" and it is designed to be fast, simple, convenient, and easily extensible. It handles both small and big sites and has a flexible system for user and group permissions. All data is stored in plain text files that can be easily manipulated with standard tools, without using any databases or other external dependencies. Existing applications include a blogging engine with RSS/Atom feeds, a wiki system that can easily integrate pre-existing documents (can be enabled for any directory tree), and others.

m9u is a music server, similar to mpd or xmms2. It
sits in the background, waiting for commands to be
delivered via a 9p file system. m9u embraces the
Unix philosophy of doing one thing well. As such,
it does not try to catalog or otherwise organize
music, but aims for the more humble goal of simply
playing it. A side effect of this approach is that
m9u is trivially extensible to domains aside from
music (for example, an image slideshow).

spectrwm is a minimalistic tiling window manager that tries to stay out of the way so that valuable screen real estate can be used for much more important stuff. It has sane defaults and does not require one to learn a language to do any configuration. It was written by hackers for hackers and it strives to be small, compact, and fast.

fluks (Free LUKS) is a disk encryption utility
that uses a master key to encrypt data, and a
number of passphrases to decrypt that master key.
It was created because of the limitations in
cryptsetup and supports more hashes, ciphers, and
cipher block modes.